Deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability observed with Atmospheric Infrared Sounder (AIRS)

Abstract

The Asian summer monsoon anticyclone is linked to climatological deep convection over Southeast Asia, and the coupling of circulation and convection strongly influences constituent behavior in the upper troposphere – lower stratosphere (UTLS). This work explores the variability of the Asian monsoon circulation and trace constituents linked to transient deep convection, on the basis of dynamical fields and outgoing longwave radiation (OLR) data, plus water vapor and ozone retrievals from the Atmospheric Infrared Sounder (AIRS) instrument. Within the monsoon region, transient deep convection varies with a timescale of ∼10–20 days, linked to active/break cycles in the monsoon circulation. We show that these convective events trigger variations of the anticyclone itself, with strong correlations between OLR and the area of low potential vorticity (PV) defining the anticyclone. Relatively high PV (stratospheric air) is also advected to low latitudes to the east of the anticyclone following enhanced convection. AIRS data show that the transient convective events are associated with the vertical transport of low ozone and high water vapor into the UTLS region, with significant effects over potential temperature levels 340–360 K (∼7–13 km). Idealized transport calculations are used to demonstrate that constituent anomalies are confined within the upper tropospheric anticyclone, and this confinement contributes to the climatological constituent patterns observed during summer.